The present application relates to a magnetic tape cartridge and a magnetic recording and reproducing apparatus used to record digital data. More particularly, the present application relates to a structure of a hub in a magnetic tape cartridge and a structure of a hub driving portion in a magnetic recording and reproducing apparatus that define the height position of the hub.
Among streamers used as external storage apparatuses for computers, so-called scan-type streamers which include a rotary drum and a tape loading mechanism and utilize a magnetic tape cartridge, similarly to video tape recorders, are commercially available. In the so-called low-end market, formats, such as DDS and DAT 72, are widespread, and there is a demand to increase the storage capacity. In order to meet this demand, manufacturers have made improvements in streamers.
For example, one method for increasing the storage capacity is disclosed in Japanese Unexamined Patent Application Publication No. 2006-107542. In this method, it is possible to use a new magnetic tape cartridge that contains a magnetic tape having a tape width larger than the width of magnetic tapes in current magnetic tape cartridges.
Unfortunately, increasing the tape width involves making substantial changes to the mechanism in the magnetic recording apparatus. Therefore, it is not practical, as a measure to achieve a larger storage capacity, to increase the tape width in accordance with the format generation.
Accordingly, the storage capacity may be increased by increasing the track density, as in the related art, or by shortening the recording wavelength so as to increase the volume of data to be recorded in one track in helical scanning.
Considering that streamers of at least the previous generation are still used and that many magnetic tape cartridges of the previous generation in which information was recorded by the previous streamers remain, it is desirable to ensure that new types of streamers capable of using new magnetic tape cartridges with a higher recording density are compatible with magnetic tape cartridges of the previous generation, are able to use magnetic tape cartridges of at least the previous generation, and can normally reproduce data recorded in the magnetic tape cartridges by streamers of the previous generation.
In a so-called DDS- or DAT-format tape streamer, if the track density is increased to realize a larger storage capacity, a hub around which a tape is wound is free to move in the height direction (up-down direction), and therefore, vibration in the height direction of the hub is caused by running of the tape. Due to this vibration, the height of the running tape changes, and the height position where the tape slides on a rotary drum having a recording and reproducing head changes. Consequently, it is difficult to precisely trace a track pattern.